It is known that improvements in vehicle performance and fuel consumption can be achieved through improvements in the aerodynamic structure of a vehicle. Such improvements are sought in the design of vehicles in the haulage industry, for example articulated vehicles of the kind having a cab and trailer.
One method of improving the aerodynamic structure of a trailer of a haulage vehicle is to modify the roof of the trailer so that it defines a recess having a surface inclined downwardly below the level of the roof at the rear of the trailer, see for example the trailer shown in GB2271323. However, the incorporation of such a recess can be complex and costly.